Which of the following acts as a strong reducing agent? (Atomic number : Ce=58,Eu=63, Gd=64,Lu=71)Lu3+Gd3+Eu2+Ce4+

The reducing agent is the one that donates electrons or reduces the other substance in a redox chemical reaction. In the lanthanide series, the most common oxidation state is +3, but some elements like cerium and europium can have +4 and +2 states respectively.

The ability of an element to act as a reducing agent depends on how easily it can lose electrons. The easier it is for an element to lose electrons, the better a reducing agent it is.

In the given options, Eu2+ can easily lose 2 electrons to achieve a stable +3 state, making it a strong reducing agent. Therefore, Eu2+ acts as a strong reducing agent among the given options.